ConcernedApe, the developer of Stardew Valley, announced via Twitter that split screen co-op will be added to Stardew Valley. This should be in the next major patch, patch 1.5.
Multiplayer is already in the game, but playing together on the same console is not yet possible. It is not known exactly when patch 1.5 will be released, but this news makes the wait a lot more difficult.
In Stardew Valley 1.5, there will be splitscreen co-op! pic.twitter.com/n7XhPWSuSi
— ConcernedApe (@ConcernedApe) October 16, 2020